1. Field of the Invention
This invention relates broadly to surgical implants. More particularly, this invention relates to bone fracture and soft tissue fixation systems for use at a metaphysis.
2. State of the Art
Fracture to the metaphyseal portion of a long bone can be difficult to treat. Improper treatment can result in deformity and long-term discomfort.
By way of example, a Barton's fracture represents a fracture dislocation or subluxation of the wrist in which the dorsal or volar rim of the distal radius is displaced relative to the carpal bones. However, volar involvement is more common. As another example, a Colles' fracture is a fracture resulting from compressive forces being placed on the distal radius, and which causes backward or dorsal displacement of the distal fragment and radial deviation of the hand at the wrist. Often, a Colles' fracture will result in multiple bone fragments which are movable and out of alignment relative to each other. If these fractures are not properly treated, permanent wrist deformity may result, as well as limited articulation of the wrist. It is therefore important to align the fracture and fixate the bones relative to each other so that proper healing may occur.
Alignment and fixation of a metaphyseal fracture (occurring at the extremity of a shaft of a long bone) are typically performed by one of several methods: casting, external fixation, pinning, and plating. Casting is non-invasive, but may not be able to maintain alignment of the fracture where many bone fragments exist. Therefore, as an alternative, external fixators may be used. External fixators utilize a method known as ligamentotaxis, which provides distraction forces across the joint and permits the fracture to be aligned based upon the tension placed on the surrounding ligaments. However, while external fixators can maintain the position of the wrist bones, it may nevertheless be difficult in certain fractures to first provide the bones in proper alignment. In addition, external fixators are often not suitable for fractures resulting in multiple bone fragments. Pinning with K-wires (Kirschner wires) is an invasive procedure whereby pins are positioned into the various fragments. This is a difficult and time consuming procedure that provides limited fixation if the bone is comminuted or osteoporotic. Plating utilizes a stabilizing metal plate typically placed against the side of a bone, and screws extending from the plate into holes drilled in the bone fragments to provide stabilized fixation of the fragments. However, many currently available plate systems fail to provide desirable alignment and stabilization.
The distal radius exhibits a concave shape extending from the shaft, which reaches an inflection point at a so-called watershed line followed by a convex like form at its most prominent feature, the volar rim. With a distal radius fracture, the complex shape of the distal radius, including the prominent volar rim of the lunate fossa, relatively flat volar rim of the scaphoid fossa, and the sometimes prominent base of the styloid process should be accommodated. Furthermore, the ligaments extending from the volar side of the distal radius to the intercarpal bones must not be irritated or distressed. Moreover, a fixation device should provide desirable alignment and stabilization of the bone structure proximate the articular surface of the distal radius.
Co-owned U.S. Pat. No. 7,250,053 to Orbay discloses a volar plate for the distal radius that accommodates the anatomy. The plate includes a head for placement at the metaphysis and a shaft for extension along the diaphysis. The head and shaft each include holes for receiving fasteners to couple the plate to the bone. The holes in the head are threaded fixed angle holes oriented to extend the shaft of the fasteners in a spatial distribution through the bone about the articular surface to provide significant support and early mobility. In addition, the top portions of the plate are such that they provide a buttress support for the fragment while providing a smooth contour to minimize soft tissue interaction and not creating a prominent sharp edge nearest the inflexion point or ‘watershed line’ of the volar rim. This is achieved by a contoured shape that blends back into the anatomy without extending into the articular surface. The lower surface of the ulnar side of the head of this plate is contoured to accommodate the concave shape of the distal radius below the watershed line. It is specifically indicated that the watershed line is not to be violated by the plate.
However, volar ulnar facet fractures occur in the distal portion of the concave form of the distal radius and require additional fixation. The fractures may involve displaced avulsions, shear fractures and small fragments that are in the vicinity of the prominent portion of the volar rim. These fractures are difficult to treat with existing hardware since most available hardware could interfere with surrounding soft tissue and/or increase the likelihood impinging on the articular surfaces of the distal radius.
U.S. Pub. No. 20090275987 to Graham proposes various plates and adjunct extenders that can be physically attached to the plates with screws to provide supplementary anatomical support. The extenders are not ideally shaped to limit interference with soft tissue. In addition, this type of support requires the attachment of very small plates to the primary plate and can be difficult to work with, particularly in the operating room and during a surgical procedure. There is no easy and reliable way to fit the extenders to the anatomy during the procedure.
Co-owned U.S. Pub. No. 20130204307 to Castaneda describes a volar rim plate that includes integrated tabs that extend over the volar ulnar facet to provide a buttress support thereover. The tabs can be readily re-orientated to approximate the volar rim and provide close support. In order to re-orient the tabs, the tabs are provided with a respective lower recess, that allows each tab to be contoured independently to fit the patient anatomy. Each tab is provided with a hole sized to closely receive a K-wire that permits the K-wire to apply a bending load to a tab in situ to bend the tab about its lower recess into a new orientation to best match the patient anatomy and provide support. Therefore, the plate does not require a dedicated bender. In addition, the hole in each tab is spaced relative to the distal peripheral edge of the tab to accommodate passage of a suture needle completely therethrough. With the tab slightly spaced from the volar rim, the suture needle can be passed through the gap between the tab and the volar rim and then through soft tissue to join the soft tissue to the plate; i.e., to facilitate repair of the joint capsule. However, such repair can result in the tab being slightly displaced from the volar rim, which may not be ideal.